Warm mix asphalt binder compositions containing lubricating additives

ABSTRACT

The present invention provides a functionally dry warm mix asphalt binder composition modified with lubricating agents or additives that can be mixed with aggregate and compacted at temperatures substantially below asphalt binder compositions that do not contain the disclosed lubricating additives.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/112,815, filed on May 20, 2011, now U.S. Pat. No. 8,323,394; which isa continuation of U.S. application Ser. No. 12/896,570, filed on Oct. 1,2010, now U.S. Pat. No. 7,968,627; U.S. application Ser. No. 12/896,532,filed on Oct. 1, 2010, now U.S. Pat. No. 7,981,952; and U.S. applicationSer. No. 12/896,488 filed on Oct. 1, 2010, now U.S. Pat. No. 7,981,466;which is a divisional of U.S. application Ser. No. 11/871,782, filed onOct. 12, 2007, now U.S. Pat. No. 7,815,725; which claims benefit to U.S.Provisional Application No. 60/976,141 filed on Sep. 28, 2007, and U.S.Provisional Application No. 60/970,809 filed on Sep. 7, 2007, all ofwhich are incorporated herein by reference in their entirety.

BACKGROUND

International Application No. WO 2007/032915, incorporated by referenceherein, reports a warm mix asphalt binder composition and process thatinjects a foaming, lubricating aqueous solution into a stream of asphaltcement prior to incorporation of the asphalt cement plus foaming,lubricating solution with aggregate at reduced temperatures to produce awarm mix asphalt paving mixture. Evaluations of warm mix compositionsproduced with this process provide a basis for the warm mix compositionsand processes disclosed in this application.

SUMMARY

The present invention provides functionally dry warm mix asphalt bindercompositions, polymer modified asphalt binder compositions orpolymer/acid-modified asphalt binder compositions that have beenmodified with lubricating non-aqueous surfactants, non-surfactantadditives or acids or combinations thereof (collectively, lubricatingagents or additives). The term “functionally dry” as used herein inconnection with compositions, aggregates or mixtures is used to describereduced water content compositions, aggregates or mixtures, particularlythose in the “warm mix” regime, as further described herein. Thementioned lubricating non-aqueous surfactants, non-surfactant additivesor acids, such as phosphoric acid additives, provide asphalt bindercompositions that can be adequately mixed with aggregate at temperatures30-50° F. lower, even more than 50° F. lower, or as much as 100° F.lower than a substantially similar asphalt binder or cement that doesnot contain these lubricating additives or combinations thereof. Inaddition, these asphalt/aggregate mixtures can be compacted attemperatures 30-50° F. lower, even temperatures more than 50° F. lower,or as much as 100° F. lower than a substantially similarasphalt/aggregate mixture that does not contain a lubricating additiveor combinations thereof. Another meaning for the term “functionally dry”as used herein is “essentially water-free” as described in the detaileddescription.

The asphalt binder compositions and aggregate mixtures that containlubricating agents or additives disclosed in the present application mayalso include liquid antistripping additives used in conventionalasphalt/aggregate mixtures.

Methods of preparing the present asphalt binder compositions as well asmethods of using the present asphalt binder compositions mixed withaggregate to prepare paved surfaces are also disclosed in thisapplication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph plotting measured viscosity and normal forceproperties with respect to velocity as a measure of lubricity of anasphalt cement and an asphalt cement modified with a lubricatingsurfactant.

FIG. 2 is a graph plotting measured viscosity and normal forceproperties with respect to velocity as a measure of lubricity of anasphalt cement and two asphalt cements modified with a lubricating wax.

FIG. 3 is a graph plotting the measured viscosities and normal forceswith respect to velocity as a measure of lubricity of an asphalt cementat three different temperatures.

FIG. 4 is a graph plotting the measured viscosity and normal forceproperties with respect to velocity as a measure of lubricity of anasphalt cement, a related polymer-acid modified asphalt cement furthermodified with polyphosphoric acid, a polymer-acid modified asphaltcement further modified with a liquid antistripping additive and apolymer-acid modified asphalt cement further modified with a lubricatingsurfactant.

DETAILED DESCRIPTION

Earlier work confirms that laboratory compaction of field-produced warmmixes utilizing the reported foaming, lubricating solution can beadequately compacted at temperatures approximately 30-50° F. or morebelow typical hot mix asphalt compaction temperatures days after fieldproduction. Testing of mix samples taken at the paver have shown thatthis mix contains approximately 0.5 wt %, or less, water which is anamount of water being well below the amount of water generally utilizedin conventional warm mix production. The only component of the foaming,lubricating solution remaining with the asphalt mixture is an effectiveconcentration of the surfactant providing the lubricating effect. Thisobservation indicates that the incorporation of water in conjunctionwith a foam for the production of warm mix is not an essential componentin all instances, although the water may be used in a system fordelivery of the lubricating additive into the asphalt binder or cement.The present invention thus relies, in part, in determining that thelubricating properties of additives added to an asphalt binder or cementare an important component of the present warm mix asphalt mixtures andthat it is not necessary or essential to use foamed asphalt binders oremulsified asphalt binders that are used in conventional warm mixasphalt binder compositions, mixtures and paving processes.

As used in the present application, each of the terms “functionally dry”or “essentially water-free” means or is intended to refer to an asphaltbinder composition that contains less water or moisture than isroutinely used in conventional or known warm mixes. This term does notmean and is not intended to refer to a warm mix composition that iscompletely free of water, moisture or added water. For example, it iswell known that aggregate that will be mixed with the present asphaltbinder compositions will also contain varying amounts of water and thatwater may affect the aggregate coating process. In embodiments of thepresent invention it is acceptable that there is some moisture containedin the aggregate, because a completely dry aggregate is not practical ormay not be desirable. The amounts of water or moisture in the aggregatewill vary for any number of reasons including but not limited to theparticular geographical region where the aggregate is crushed orstockpiled, the local weather conditions, the local temperature of theparticular stockpile facilities. Due to this variation in the watercontent of the aggregate, it is expected that there may be adjustmentsmade to the actual water content of the asphalt binder compositions ofthis invention before the aggregate is coated with the asphalt mixturein order to achieve acceptable coating of the aggregate. If theaggregate is either very wet or very dry the water the water content ofthe aggregate may be adjusted or altered or, alternatively, the water ormoisture content of the asphalt binder composition may be adjusted oraltered in order to optimize or ensure adequate coating of the aggregateduring mixing. Warm mixes of the present invention will generallyinclude about 2-9 wt % asphalt binder composition and about 91-98 wt %aggregate. In other embodiments, the warm mixes will include about 3-8wt % asphalt binder composition and about 92-97 wt % aggregate.asphalt/aggregate. The amount of asphalt binder composition requiredwill depend upon mix type, layer in the pavement structure, aggregatesize or traffic considerations, among other factors.

The moisture content of the asphalt binder composition may be changed ina number of ways such as injecting or spraying water into the asphaltbinder compositions. Even though the asphalt binder compositions mayhave the water or moisture content adjusted or altered, thesecompositions are considered to be functionally dry because the overallwater content is lower or substantially lower than other known orconventional warm mix asphalt binder compositions and mixtures.

In addition, it is well known that different grades of asphalt will havedifferent mixing properties and conditions. Adjustments or alterationsof the water or moisture concentrations that take into account differentasphalt grades are also considered to be functionally dry (oressentially water-free) asphalt binder compositions. When variations inthe water contents of different aggregates and different asphalt gradesare accounted for, the asphalt/aggregate mixes of mixtures of thepresent invention will typically have a water content in a range of lessthan about 5 wt %. In many instances the water content is less thanabout 1 wt %. In certain embodiments of this invention, the asphaltbinder compositions comprise less than 0.5 wt % water. It is understood,however, that water contents outside this range would still be withinthe scope of the present claims and embodiments of the invention whenthe claimed compositions contain the lubricating agents or additives,including the non-aqueous surfactants, non-surfactant additives andacids, disclosed in this application.

This application discloses that surfactants in both aqueous ornon-aqueous form and waxes are two general classes of lubricatingadditives that may, when incorporated into an asphalt binder or cementat levels as low as 0.1 wt %, provide sufficient lubrication of theasphalt cement so that aggregate may be adequately coated attemperatures 30-50° F. lower, even more than 50° F. lower, or as much as100° F. lower than the temperatures normally needed to produce abituminous mixture without an added lubricating additive or agent. Thelubricating additive then enables compaction of these mixtures at 30-50°F. lower, even more than 50° F. lower, or as much as 100° F. lower thanthe temperatures normally needed for compaction of similar bituminousmixtures.

Non-aqueous surfactants as additives have been commonly incorporatedinto asphalt cement to provide improved moisture resistance, however,their value and function as a lubricating agent in warm mix asphalt andspecifically as a functionally dry or water free warm mix compositionhave not been readily apparent to those skilled in the art prior to thedisclosure of the elements and examples of this invention and theinvention referenced in U.S. Provisional Application No. 60/976,141 andU.S. Provisional Application No. 60/970,809. Suitable lubricatingsurfactants as additives include naturally occurring compounds and morecommonly synthesized chemical compounds from three categories ofsurfactants: detergents, wetting agents and emulsifiers. Surfactantadditives may be specifically grouped into four classifications: i)anionic surface agents to include, but not limited to, fatty acids(saturated and unsaturated fatty acids), fatty acid pitch (stearic acidpitch), and fatty acid derivatives (fatty acid esters and fatty acidsulfonates), organo phosphates (alkyl phosphates); ii) cationic surfaceagents to include, but not limited to, alkyl amines, alkyl quaternaryammonium salts, heterocyclic quaternary ammonium salts, amido amines,and non-nitrogenous sulfur or phosphorous derivatives; iii) ampholyticsurface agents to include, but not limited to, amino acids, amino acidderivatives, betain derivatives (alkylbetains and alkylaminobetains),imidazolines, imidazoline derivatives; and iv) non-ionic surface agentsto include, but not limited to, fatty acid ester bonds (SPANS andTWEENS), with surfactants ether bonds (alkylphenolpolyoxeythylenes andplyoxyethylenated alcohols), surfactants with amide bonds(alkanolamides, mono and diethanolamides and their derivatives),alkylenated oxide copolymers and polyoxyethyleneated mercaptans.

Non-surfactant additives based on wax chemistry have been incorporatedinto an asphalt binder or cement to produce warm mix based on theconcept that these wax additives reduce the viscosity of the wax asphaltblend to an extent sufficient to enable production and lay down of theasphalt/aggregate mixture at reduced temperatures. The data in thisapplication indicates that typical wax additives such as Sasobit™ wax(Sasol North America Inc.) and montan wax (Romanta, Amsdorf, Germany orStrohmeyer and Arpe, N.J.) used for this application have only a minoreffect on reducing the viscosity of the asphalt-wax blend, but suchadditives, even at usage levels well below those generally employed,provide a noticeable and beneficial lubricating effect on theasphalt-wax combination. Non-surfactant additives based on wax chemistrymay be selected from a group of paraffin and non-paraffin waxes.Paraffin waxes include, but are not limited to, petroleum derived andrefined waxes (slack wax and refined micro-crystalline wax) whilenon-paraffin waxes include, but are not limited to, natural waxes(animal and vegetable waxes e.g. bees wax and carnuaba wax), modifiednatural waxes (brown coal derivative, e.g., montan wax and mineral oilderivatives), partial synthetic waxes (acid waxes, ester waxes, amidwaxes, alcohol waxes and oxidized polyethylene waxes), or full syntheticwaxes (Fischer-Tropsch waxes and polyethylene waxes).

Other non-surfactant additives such as viscosity modifiers (VMS),dispersant viscosity modifiers (DVMS), and additives containingviscosity modifiers and/or dispersant viscosity modifiers as well asextrusion and molding production processing aids, polyolefins andsulfur, may provide lubricating characteristics to petroleum productsand may also be used as a non-surfactant additive for functionally dryor waterless warm mix asphalt formulations. Such additives include, butare not limited to, VMS and DVMS used in engine lubricating oils(polyisobutylenes, olefin copolymers, hydrogenated styrene-dienecopolymers, styrene maleate copolymers, polymethacrylates, olefin-graftPMA polymers and hydrogenated polyisoprene star polymers) and productscontaining VMS and DVMS such as the residual bottoms from refinedrecycled engine lubricating oils; processing aids used in extrusion andmolding operations (high trans content polyoctenamer reactive polymer),polyolefins (ethylene vinyl acetate (EVA), acrylic polymers andsilicones); and sulfur (as sulfur impurities in fuels have been known toprovide lubrication properties).

This application also discloses that different concentrations ofphosphoric acid, are another class of additives that can, whenincorporated into an asphalt cement at levels as low as about 0.2-1.0 wt%, provide sufficient lubrication of the asphalt cement so thataggregate may be adequately coated at temperatures 30-50° F., or greaterdifference, below the temperatures normally needed to produce abituminous mixture without the phosphoric acid additives.

The following data set out in the examples below indicate that theaddition of surfactant in non-aqueous form enables utilization ofasphalt cements that have been produced using acid modifiers, typicallythose acid modifiers being those drawn from the type of polyphosphoricacid (PPA) or superphosphoric acid (SPA), although other grades ofphosphoric acid and other types of acids, such as mineral acids, otherinorganic acids or organic acids, may be utilized with the presentinvention.

While not intending to be bound by theory, the present invention isbased, in part, on the observations that the lubricating agents andadditives disclosed in this application provide a warm mix havingdesired visco-lubricity characteristics or properties. As used in thisapplication the term “visco-lubricity” means a characteristic of amaterial that it exhibits under high rotational velocity as the gapthickness of the material being tested approaches zero. As the gapthickness is reduced and as rotational velocity is increased, thematerial's viscosity begins to decrease but the normal force between theplates begins to increase. A material that has good visco-lubricitycharacteristics will exhibit less normal force increase than one whichhas poor visco-lubricity. Stated another way, the ability of thematerial being tested to enable the plates to easily rotate relative toeach other becomes more important than the viscosity of the materialbeing tested. An example illustrating the meaning of the term“visco-lubricity” is the observed reduced requirements for the mixingand compaction temperatures of polymer modified asphalt binders comparedto conventional asphalt binders. Based on purely viscosity data, polymermodified binders should require mixing and compaction temperatures thatare 20-50° F. higher than those which common practice have found to beadequate. Many studies have been conducted to explain this apparentcontradiction however none have proven wholly satisfactory. It is nowbelieved that these polymer systems are creating a lubricated asphaltbinder having visco-lubricity properties that provide adequate mixing tocoat aggregate particles and further provide mix compaction attemperatures substantially below those predicted based on viscosityalone.

Another example illustrating the meaning of the term visco-lubricity isthe reduction in dry tensile strength of many mixtures produced usingconventional asphalt binders combined with liquid antistrip orantistripping additives. Those skilled in the art of performing tensilestrength ratio (TSR) tests to verify that bituminous mixtures will notbe water sensitive, have seen that the dry tensile strength of mixturesusing antistrip treated binders can be noticeably lower than the drytensile strength of the same mix produced with the same binder butwithout antistrip. This observation has typically been attributed to areduction in binder viscosity or stiffness due to the addition of theantistrip to the binder. However, there is often minor reduction inviscosity or stiffness when low levels of antistrip are added to thebinder. It is now believed that this tensile strength reduction is anexample of the antistrip lubricating the mix resulting in the observedreduced dry tensile strength. A typical recent example will serve tomake the point.

A PG 58-28 with and without antistrip was used to produce a mix fortensile strength ratio testing according AASHTO test method T-283.Rheological properties of the PG 58-28 with and without the antistripwere determined. All results are shown in Table 1. For these particularsamples there is actually a slight increase in stiffness after theaddition of the antistrip (6.3% increase) and yet the dry tensilestrength of the mix with the antistrip is reduced by 22.7% based on theaverage values of the two results using the PG 58-28 without antistrip.The wet strength is reduced by only 8.4%. This reduction in dry tensilestrength, which does not occur with all mixes and all binders, iscertainly a common response observed by asphalt mix design technicians.Based on the present warm mix work and lubricity testing disclosedherein, the dry tensile strengths are being reduced due to thelubricating effect of antistripping additive. The specimens tested forwet strength are typically saturated to a level of 60 to 80%. Thereduced strength of saturated mixes without antistrip is typicallyattributed to debonding of the binder from the aggregate, whichtypically can be visually verified. When an antistrip functions asdesired there is little or no visual debonding of binder from theaggregate, but it must be considered that reduction in wet strength ofthe antistrip treated mixes is beginning at the reduced value indicatedby the dry strength of the antistrip treated mixes due to thelubricating effect of the antistrip.

TABLE 1 DSR, Complex G*/sin(δ) viscosity Dry Wet % @ @ 58° C., Strength,Strength, Sample AC 58° C., kPa Pa · s PSI PSI TSR 58-28, no 5.5% 1.33133 78.2 51.9 66.4% antistrip 58-28, no 5.8% 1.33 133 72.4 47.7 65.9%antistrip 58-28, 5.6% 1.42 142 58.2 45.6 78.4% 0.3% antistripLaboratory Testing of Lubricity

Since there are no readily available rheological tests identified fordetermining the lubricity of asphalt cement, the following test providescomparative testing of asphalt cement at different temperatures and withdifferent additives to determine lubricity. This test is described asfollows.

1. An AR2000 dynamic shear rheometer using a heated air test chamber wasutilized.

2. A shallow cylindrical cup measuring approximately 35 mm in diameterwith and approximately 5 mm in height was used to contain the liquidbeing tested. This cup was secured to the bottom pedestal of the testfixture in the rheometer.

3. A small quantity of the asphalt cement or asphalt cement pluslubricating additive was added to the bottom of the cup. A 25 mmdiameter flat plate was used as an upper test fixture in the rheometer.This upper test fixture is a typical test fixture used in plate-platerheological testing with this instrument.

4. The plate attached to the upper text fixture is brought into contactwith the specimen in the cup and the gap is reduced until a membrane ofmaterial to be tested is either 100 or 50 μm thick.

5. The test we used is a steady shear test with increasing velocity. Thespecimen is maintained at a constant temperature while the upper platerotates in one direction with a programmed increase in angular velocity.As the rotational speed increases the drag between the upper plate andthe bottom of the cup increases. In addition normal force increasesattempting to force the plates apart. The more lubricating character anadditive has the lower the normal force buildup.

In reference to Figures, the upper sets of plotted data are forviscosity, while the lower sets of plotted data are for normal force.

Example 1 and Data Represented in FIG. 1

A neat PG 58-28 asphalt cement was tested as described above at 90° C.(194° F.) as being representative of a low end, but not uncommon, warmmix asphalt compaction temperature. A material thickness of 100 μm wasused. FIG. 1 illustrates that, as the test velocity increases, theviscosity of the material is nearly steady and then begins to graduallydecrease until a point is reached where the viscosity decreases veryrapidly. For the neat PG 58-28 (black solid diamonds) the normal forcebegins to increase at a velocity of approximately 50 radians/sec. As thetest velocity increases the normal force increases for the neat asphaltuntil the endpoint of the test is reached. The normal force increases toapproximately 2.7 newtons. Several different additives and usage levelsare compared in this plot. Two different tests of the PG 58-28 with 1.5wt % Sasobit™ wax are shown, the open and solid circles. In one test(the open circle) the normal force reached a value of approximately 1.2newtons before the test terminated. In the other test (solid circles)the normal force reached about 0.4 newtons. Two tests at a usage levelof 0.5 wt % Sasobit™ wax are also shown (open and solid squares). Inboth of those tests the maximum normal force never exceeded 0.4 newtons.Lastly, E-6, an ethoxylated tallow diamine (Akzo Nobel Co.), was addedat 0.2% by weight to the PG 58-28 and tested (open diamond). This sampleachieved a maximum normal force of approximately 0.7 newtons beforedecreasing. For all blends it is possible to observe that the viscosityof the neat asphalt and the asphalt plus additives is similar from blendto blend for low to medium velocities. The normal forces are alsosimilar until the test velocity becomes quite high. Then the blends withthe additives exhibit lower normal forces and in several instances thenormal force values peak and then diminish. The data in this plotsupports the assertion that (1) the addition of wax additives such asSasobit™ wax do not appreciably diminish the viscosity in the low tomedium velocity ranges of the asphalt cement at warm mix compactiontemperatures (regardless of dosage level) and (2) the addition of thewax additive does provide evidence of lubricating the blend compared tothe control, neat PG 58-28.

Example 2 and Data Represented in FIG. 2

To better differentiate between neat asphalt and asphalt containinglubricating additives, the gap in the testing fixture was reduced to 50μm. FIG. 2 illustrates the normal force comparison of neat PG 58-28(open circles), 1.5 wt % Sasobit™ wax (open squares), 1% montan wax(solid squares) and 0.5 wt % Sasobit™ wax (solid circles). The normalforce for the neat PG 58-28 increases to approximately 8 newtons at 100radians/second. The normal force for the 1.5 wt % Sasobit™ wax increasesto approximately 5.5 newtons before decreasing. Both the 1 wt % montanwax and 0.5 wt % Sasobit™ wax only reach a normal force maximum of about3 newtons. For all of these blends note that the viscosities of thevarious samples are very nearly identical in the low and medium velocityranges, indicating that the wax additives are not functioning by amechanism of decreasing the viscosity of the asphalt and wax blends.

Example 3 and Data Represented in FIG. 3

A common way to achieve properties suitable for an asphalt cement thatenable it to be compacted is to increase its temperature. FIG. 3illustrates the variation in viscosity and normal force for a neat PG58-28 at 3 different temperatures; those temperatures being 90° C. (194°F.), 100° C. (212° F.) and 125° C. (257° F.). FIG. 3 illustrates that asthe temperature increases the viscosity decreases, as would be expected.FIG. 3 also illustrates that between a test velocity of 10 and 20radians/second the normal force begins to increase. As the testtemperature increases the normal force peak shifts to lower values atever increasing velocity values. At 100 radians/second the 90° C. sampleexhibits a normal force of about 9 newtons, the 100° C. sample exhibitsa normal force of about 4.5 newtons and the 125° C. sample exhibits anormal force of just under 2 newtons. It is instructive to realize thattypical hot mix asphalt materials are initially compacted in the rangeof 125° C. but are not initially compacted at 90° C. This data indicatesthat warming a PG 58-28 provides lubricating properties in the binderthat are acceptable for compaction, whereas typically contractors wouldnot allow a paving mix to cool to a temperature as low as 90° C. beforebeginning compaction. Therefore hot mix and warm mix are on a continuumline of temperature and it is the nature of the additives that enablewarm mix materials to be compacted adequately at temperatures in the90-100° C. range.

Example 4 and Data Represented in FIG. 4

Example 4 illustrates the impact of polyphosphoric acid (PPA) plus otheradditives on the reduction of normal force buildup in the asphaltbinder. A polymer modified PG 58-34 which also contains PPA as areactant was tested in duplicate (open and solid circles). Additionally0.5 wt % INNOVALT W phosphate ester antistripping material was added tothe PG 58-34 and tested and in another sample 0.3 wt % ethoxylatedtallow diamine was added to the PG 58-34. All of these samples werecompared to a standard PG 58-28. All tests were conducted at 90° C. witha 50 μm test gap. The data plotted in FIG. 4 indicate that even thoughthe viscosity of the 58-34 and its blends (upper curves on the plot) aregreater than the viscosity of the PG 58-28, the normal force values areuniformly lower at 10 radians/second and higher. The INNOVALT W added tothe PG 58-34 showed the greatest reduction in normal force build-up, butthe PG 58-34 with just the acid additive also showed surprisingreduction in normal force relative to a neat, unmodified binder. Insummary, PPA at typical usage levels (0.2 to 1 wt %) can serve as alubricating additive in the production of warm mix asphalt bindercompositions.

Example 5

A PG 64-28 asphalt binder was made by blending 0.75 weight percentpolyphosphoric acid with a PG 58-28 asphalt cement. To this blend wasadded 0.5 wt % phosphate ester antistripping additive and 0.2 wt % ofE-6 ethoxylated tallow diamine. This asphalt binder blend was mixedusing no water at 230° F. with a gravel aggregate. A 100% coating wasachieved of the aggregate at this temperature. The mix was compacted toproduce Hamburg rut testing specimens at 230° F. achieving the densityvalues expected of a hot mix asphalt.

One test of a paved material's performance is to simulate vehicletraffic stress by the number of repetitive passes a roller supporting aspecified weight load must make to cause formation of a rut of aspecified depth in the material. Such testing of compacted materialproduced by the inventive process was done using a testing machinereferred to as a Hamburg Wheel Tracking (“HWT”) Tester, also known as aPMW Wheel Tracker, available from Precision Machine and Welding, Salina,Kans. The number of Hamburg passes required to reach a rut depth of 10mm when the compacted material tested in a dry condition was used forcomparative evaluation. The test conditions were 158 lb. wheel load, 52passes per minute at the test temperature using heated air to achievethe specimen test temperature. Generally, when all other variables areessentially the same, the greater the number of passes, the better theanticipated paving mix performance. Those persons of ordinary skill inthe art and familiar with the HWT will recognize paving materials thatare suitable for a particular application based on the results that areprovided when samples are subjected to these test conditions.

Rut tests were performed on specimens produced as identified above usingcompletely dry aggregate and compared to rut tests performed onspecimens produced using the same 64-28 plus 0.5 weight percentphosphate ester plus 0.2 weight percent of E-6 introduced using a waterdispersed solution (as set out in United States Published Application2007/0191514). Hamburg rut tests were conducted at 50° C. in a waterimmersed procedure. The average number of rut passes to reach 12.5 mm ofrutting was 7300 for the specimens prepared according the procedure ofthis invention and 4176 according to the procedure using the aqueous,foaming lubricating solution. Further the binders from specimens fromeach rut test were extracted and recovered and the rheologicalproperties determined at 64° C. The PG 64-28 plus 0.5 weight percentphosphate ester antistrip had a test value for G*/sin(delta) of 1.12kiloPascals at 64° C. The binder recovered from the mixture producedusing the foaming, lubricating solution had a test value of 1.27kiloPascals and the binder recovered from the mixture produced using theprocedure of this invention had a test value of 1.99 kiloPascals.Normally one would expect the value of G*/sin(delta) to increase as aresult of mixing and recovery. While there was a slight increase usingthe foaming lubricating solution it is most likely that a moresubstantial increase was counteracted by the interaction of thepolyphosphoric acid with the water from the foaming solution and thebasic character of the dispersed E-6 diamine. By adding the E-6 innon-aqueous form as per this invention the value of G*/sin(delta)increased to greater and more typical extent while still maintaining theability of the mixture to be produced and compacted under warm mixconditions. The above further supports the embodiment of the presentinvention for the production of warm mix using binders containing acidmodifiers.

Example 6

A field trial using 300 tons of mix that was produced from PG 58-28asphalt binder with 0.3 wt % polyamine antistripping additive and 0.3 wt% E-6 ethoxylated tallow diamine added. This mix was made at acounterflow drum mix plant and placed on a private road. The mixcontained 20% RAP and warm mix was produced at a temperature of about220-240° F. Compaction took place at temperatures ranging from 205-220°F. Typical hot mix temperatures for this same mix were 310° F. mixtemperature and initial compaction temperatures in the range of 285° F.and higher. Field cores obtained one day after mix laydown andcompaction showed results of 93.3% and 93.8% of maximum theoreticaldensity. The target density for this mix by specification is 92.0% orgreater.

Example 7

A field trial consisting of 700 tons was conducted using a PG 58-28binder with 0.3 wt % polyamine antistripping additive and 0.3 wt % E-6ethoxylated tallow diamine added. This blend was mixed with a limestoneaggregate through a counterflow drum mixing facility. Warm mix wasproduced at temperatures varying from 210° F. to as high as 260° F. dueto plant variations caused by low production rates during the trial.However, when the mix discharge temperature was stabilized at 225° F. to235° F. the coating of the aggregate was at 100%. This mixture wasfurther taken to an on-going road project and successfully paved attemperatures ranging from 225° F. to as low as 200° F. Cores cut fromthis trial pavement exhibited in place densities of 90.8%, 91.6%, 92.2%,91.2%, 92.1% and 94.0% with values of 91-92% being typical for in placedensities when this type of mix is placed as a hot mix. The mixtureproduced during this trial contained 20 wt % reclaimed asphalt pavement(RAP). This is significant because the utilization of RAP is animportant component of the Hot Mix Asphalt (HMA) paving industry.Although the top end amount of RAP in warm mix is a matter of choice, anamount could be greater than about 50 wt % because of the requirementthat the warm mix discharge temperature be kept low relative toconventional HMA. This same mixture when produced as a conventional hotmix asphalt was mixed at a temperature of 300-310° F. and compacted attemperatures approximately 15-20° F. cooler than the mix temperature.

Example 8

A field trial was conducted using a PG 58-28 binder with 0.3 wt %polyamine antistripping additive and 0.3 wt % E-6 ethoxylated tallowdiamine added. This blend was then mixed with aggregate containing 30 wt% RAP at mixing temperatures ranging from 220-240° F. Compaction tookplace at temperatures ranging from 205-225° F. After this asphalt bindercomposition was mixed with aggregate, applied and compacted the pavementdensities were determined using standard industry procedures.

The following densities were measured.

1 foot off center line—95.4% of maximum theoretical density

6 feet off center line—94.7% of maximum theoretical density

Shoulder of road paved over crushed aggregate base—92.5% of maximumtheoretical density

The two pavement densities were taken on pavement sections paved overconventional hot mix asphalt. Typically the first layer of mix pavedover aggregate has lower densities because the underlying structure isnot as rigid. Target mix density for the mix over pavement is 92% orhigher and the density for shoulder mix over crushed aggregate is 91% orhigher. This warm mix sample had measured physical properties that wereabove minimum properties for conventional heat mix samples.

Example 9

A treated asphalt binder composition of PG 58-28 binder modified withE-6 ethoxylated tallow diamine surfactant and polyamine antistrippingadditive was added to a tank that had held an untreated asphalt. As amix with aggregate containing 30 wt % RAP was beginning to be made, theuntreated binder in the tank was first pumped into a mixing drum at warmmix temperatures. This untreated binder did not produce a coatedasphalt/aggregate mix. After some time when the treated binder was beingeventually incorporated into the mix, good coating in the 220-240° F.temperature range was achieved. Approximately 700 tons of this warm mixwas placed and compacted in the field at temperatures ranging from about212-228° F. A sample of this mix was taken for moisture contentdetermination just as the mix was discharged from the mixing drum at adischarge temperature of about 235° F. The sample was placed in aplastic container and sealed. Within 30 minutes this sample was testedfor moisture content using a solvent refluxing procedure, ASTM D 1461.The moisture content of the mix was 0.25 wt %.

After this asphalt binder composition was mixed with aggregate, appliedand compacted, the pavement densities were determined using standardindustry procedures. The following densities were measured from randomlyselected samples—93.3%, 93.4% and 93.8% of maximum theoretical density.Normal hot mix produced at this plant with the same aggregate and RAPmaterials and untreated PG58-28 was mixed at 325° F. and paved atapproximately 300° F. and compacted 5-10° F. below the pavingtemperature.

Example 10

Using the same aggregate and RAP as Example 9, about 200 tons of warmmix using a blend of PG 58-28 binder, 0.5 wt % Sasobit wax and 0.3 wt %polyamine antistripping additive. A well coated warm mix containing 30wt % RAP was produced at temperatures ranging from 215-240° F. When themix was produced on the cooler end of this temperature range, there wastendency of the mix to drag due to sticking on the paver screed.However, when the mixing temperature again increased to 240° F., thedragging of the mix disappeared. This mix appeared to compactadequately.

After this asphalt binder composition was mixed with aggregate, appliedand compacted, the pavement densities were determined using standardindustry procedures. The following density was measured from a randomlyselected sample—93.0% of maximum theoretical density. The followingdensity results were determined: 92.7% on the shoulder, 93.0% in theregion where the mix was sticking, 93.4%, 93.5% and 93.3% at otherlocations on the pavement when the mixing temperature was back in the230-240° F. range. For this project shoulder density minimumrequirements were 92.0% of maximum theoretical density and mainlinepavement minimum density requirements were 93.0% of maximum theoreticaldensity.

Example 11

A laboratory mix was produced using a PG 70-22 binder modified with SBS(styrene butadiene styrene) polymer. To this blend was added 0.3%polyphosphoric acid and 0.3% PreTech Pavegrip 650 (an amine basedantistrip). The asphalt temperature was 325° F. and was being used at5.3%. The aggregate was completely dry and heated to 260° F. andverified with a certified thermometer. The mixture was put together andmixed in a bucket mixer for approximately 30 to 45 seconds. The coatingwas 100% and comparable to the hot mix version that was compactedpreviously. The heat in the bucket dropped below 240° F. before thesample was removed from the mixer. The sample was then “cured” for 2hours at 248° F. and then compacted with 37 blows per side on theMarshall Hammer compacting machine. The resultant sample had about 5.88%average air voids. Data comparing the hot mix version and warm mixversion are listed in Table 2.

TABLE 2 Compaction Binder = PG70-22 (SBS) Mix Temp Temp Blows Air Voids0.3% PPA, 0.3% AS 340 300 30 5.49 0.3% PPA, 0.3% AS 340 266 37 5.59 0.3%PPA, 0.3% AS 340 248 37 5.77 0.3% PPA, 0.3% AS 260 248 37 5.88

EMBODIMENTS OF THE INVENTION

A first embodiment of the present invention is a warm mix, functionallydry asphalt binder composition comprising a lubricating surfactant.Suitable lubricating surfactants include neutral, cationic and anionicsurfactants. One suitable surfactant is an ethoxylated tallow diaminesurfactant. In alternative embodiments of the invention, the lubricatingsurfactant may be used in an amount of about 0.1-1.0 wt % of the asphaltbinder composition.

A second embodiment of the present invention is a functionally dry warmmix asphalt binder composition comprising a lubricating wax. Suitablelubricating waxes include montan waxes, petroleum waxes or amide waxes.In alternative embodiments of the invention, the lubricating wax may beused in amount of about less than 1.5 wt % of the asphalt bindercomposition. In other alternative embodiments of the invention thelubricating wax may be used in an amount of about 0.1-0.5 wt %.

A third embodiment of the present invention is a functionally dry warmmix asphalt binder composition comprising a lubricating acid such as,for example, anhydrous phosphoric acid. Suitable lubricating phosphoricacid grades include polyphosphoric acid (PPA), superphosphoric acid(SPA), or other grades of phosphoric acid. One suitable phosphoric acidderivative is polyphosphoric acid. In alternative embodiments of theinvention, the lubricating phosphoric acid derivative may be used in anamount of about 0.2-1.0 wt % of the asphalt binder composition.

Both the first, second and third embodiments of the present asphaltbinder compositions may be mixed with aggregate at a temperature ofabout 280° F. and lower temperatures (where this mixing temperature maybe a function of the original or starting PG asphalt grade, viscosity orpenetration of the binder) and that the then resultant mixture may becompacted at a temperature of about 260° F. and lower temperatures(where this compaction temperature may also be a function of theoriginal or starting PG asphalt grade, viscosity or penetration of thebinder). Hot mix asphalt mixtures produced from the same binders notutilizing the present invention are reasonably anticipated to requirerespective mixing and compaction temperatures 70-100° F. higher thatthose temperatures stated above.

Another embodiment of the present invention is a functionally dry warmmix polymer/acid modified asphalt binder composition comprising alubricating surfactant, a lubricating wax or both.

Still another embodiment of the present invention is a functionally drywarm mix polymer modified asphalt binder composition comprising alubricating surfactant, a lubricating wax or both.

This embodiment provides a modified asphalt binder composition that canbe mixed with aggregate at a temperature that is at least 30-50° F.below, even temperatures more than 50° F. lower, or as much as 100° F.lower than the temperature that is adequate to mix a similar modifiedasphalt binder composition that does not contain a lubricatingsurfactant, a lubricating wax or a lubricating acid or combinationsthereof.

The present invention also includes forming a paved surface using thenovel warm mix composition described herein. In this aspect, a pavingmix may be made in the temperature ranges described herein using thecomposition described. The mixing typically occurs away from the pavingsite, and the mixture is then hauled to the site and supplied to apaving machine. The mixture of the lubricated asphalt binder compositionand aggregate is then applied by the paving machine to a preparedsurface after which it is usually roller compacted by additionalequipment while still at an elevated temperature. The compactedaggregate and asphalt mixture eventually hardens upon cooling. Becauseof the large mass of material in paving a roadway or commercial parkinglot, the cost of the thermal energy to achieve suitable mixing andpaving is reduced because of the reduction in the temperature necessaryin the mixture for proper paving. This will result in cost savingsattributable to the present invention because of the reduced need forthermal energy to be supplied or maintained in the mixture. For commonbinders used in the practice of the present invention, thevisco-lubricity characteristics of the binder and lubricating agentcomposition affect the temperature needed to provide thorough coating ofthe aggregate and application and compaction of the asphalt andaggregate mixture according to the present invention.

Accordingly, in one aspect, the present invention includes a pavedsurface formed using the novel warm mix composition described herein.Such a paved surface comprises a compacted mixture of an aggregate and afunctionally dry warm mix asphalt binder composition including anasphalt binder, and one or more members selected from the groupconsisting of a lubricating surfactant, a lubricating non-surfactantadditive, a lubricating acid or combinations thereof. In another aspect,the present invention includes a method of forming a paved surface usingthe novel warm mix composition described herein.

The present inventive process includes adding a lubricating substanceinto an asphalt binder heated to within a warm mix temperature range tocreate a warm mix lubricated asphalt binder composition; combining thewarm mix lubricated asphalt binder composition with a suitableaggregate; mixing to coat the aggregate with the lubricated asphaltbinder composition to form a warm mix paving material; transferring thewarm mix paving material to a paving machine; applying the warm mixpaving material with the paving machine at a warm mix paving temperatureto a prepared surface; and then compacting the applied paving materialto form a paved surface.

The invention is not to be taken as limited to the details of the abovedescription as modifications and variations may be made withoutdeparting from the spirit or scope of the invention.

The following is claimed:
 1. An asphalt paving composition comprisingfunctionally dry, essentially water-free, non-foamed asphalt bindercontaining lubricating additive comprising an anionic surfactant or anon-ionic surfactant mixed with uncompacted aggregate to provideaggregate coated with binder and lubricating additive suitable for useas a warm mix paving composition; wherein the warm mix pavingcomposition is produced at a warm mix temperature which is at least 30°F. lower than a comparison production temperature needed to produce acomparison paving composition containing binder-coated aggregate withoutthe lubricating additive.
 2. An asphalt paving composition according toclaim 1 wherein the anionic surfactant comprises saturated orunsaturated fatty acids, fatty acid pitch, or fatty acid derivatives. 3.An asphalt paving composition according to claim 2 wherein the anionicsurfactant comprises fatty acid sulfonates.
 4. An asphalt pavingcomposition according to claim 1 wherein the non-ionic surfactantcomprises a surfactant having fatty acid ester bonds, a surfactanthaving ether bonds, a surfactants having amide bonds, an alkylenatedoxide copolymer or a polyoxyethylenated mercaptan.
 5. An asphalt pavingcomposition according to claim 4 wherein the non-ionic surfactantcomprises an alkylphenoloxyethylene or a polyoxyethylenated alcohol. 6.An asphalt paving compositions according to claim 1 further comprisingan antistrip material.
 7. An asphalt paving composition according toclaim 1 wherein the warm mix paving composition is paved and compactedat a warm mix temperature at least 30° F. lower than a comparison pavingtemperature needed for proper paving of the comparison pavingcomposition.
 8. An asphalt paving composition according to claim 1wherein the warm mix paving composition is paved and compacted at a warmmix temperature more than 50° F. lower than the comparison productiontemperature.
 9. An asphalt paving composition according to claim 1wherein the warm mix paving composition is paved and compacted at a warmmix temperature more than 100° F. lower than the comparison productiontemperature.
 10. An asphalt paving composition according to claim 1wherein the warm mix paving composition when paved and compacted has acompacted density 91% or higher compared to maximum theoretical density.11. An asphalt paving composition according to claim 1 wherein theasphalt binder is a Performance Graded (PG) asphalt binder.
 12. Anasphalt paving composition according to claim 1 wherein the aggregateincludes up to 100 weight percent reclaimed asphalt pavement (RAP). 13.An asphalt paving composition according to claim 1 wherein the asphaltbinder comprises a polymer-modified, acid-modified or polymer- andacid-modified binder.
 14. An asphalt paving composition according toclaim 1 wherein the lubricating additive is about 0.1 to 1.5 weightpercent of the asphalt binder weight.
 15. An asphalt paving compositionaccording to claim 1 wherein the lubricating additive is about 0.2 to1.0 weight percent of the asphalt binder weight.
 16. An asphalt pavingcomposition according to claim 1 wherein a blend of the asphalt binderand lubricating additive has a measured maximum normal force no morethan about 5.5 Newton's at 90° C. using a dynamic shear rheometer with a50 μm gap.
 17. An asphalt paving composition according to claim 1wherein a blend of the asphalt binder and lubricating additive has ameasured maximum normal force no more than about 3 Newtons at 90° C.using a dynamic shear rheometer with a 50 μm gap.
 18. An asphalt pavingcomposition according to claim 1 wherein the warm mix paving compositioncontains less than 5 wt. % water.
 19. An asphalt paving compositionaccording to claim 1 wherein the warm mix paving composition containsless than 1 wt. % water.
 20. An asphalt paving composition according toclaim 1 wherein the warm mix paving composition contains less than 0.5wt. % water.